The main aim of this phase II proposal is to continue and complete development of a cellular phone-based system that assists patients with their medication adherence. Adherence reports will be developed with feedback from patients and providers. Software for patients to report their four day recall adherence through text messaging or short message service (SMS) or interactive voice response (IVR) will be built. An initial qualitative study will evaluate the adherence reports, 4-day adherence recalls, and inform the development of content for reminder text messages that could be resistant to user fatigue. A redesigned system will be tested through a 3-week longitudinal study of 15 patients with human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS). An intervention module will have an analytics engine to track adherence levels and personalize delivery of reminder messages. A clinic appointment module will perform patient appointment reminders. The final system with these modules will be tested through a 24-week efficacy study. A total of 115 patients and providers will be involved in the three user studies.